A Manhattan judge today threw a wrench in Mayor Bloomberg’s plans for outer borough livery cabs and the sale of 2,000 yellow cabs, which was supposed to bring the cash-strapped city $1 billion.

Judge Arthur Engoron — siding with medallion owners and taxi lenders who sued City Hall — issued a temporary restraining order barring the Taxi and Limousine Commission from proceeding with the medallion sale and the implementation of the new livery cabs.

The medallion owners and taxi lenders had filed three separate lawsuits alleging the law allowing the outer boro liveries — which the Mayor pushed to Albany to get around the City Council — was unconstitutional.

Engoron agreed.

“Both governments are democracies, but only one is solely answerable on election day to the constituents of the five boroughs, those directly affected by the taxi service at issue here,” he wrote.

He said that he was issuing the temporary restraining order because he believed the three lawsuits against the city would succeed.

Mayor Bloomberg had made the outer borough livery cabs a centerpiece in his transportation plans, saying that much of the city was underserved by yellow cabs.

The city had planned to start selling permits for the livery cabs — which could accept street hails only in the outer boroughs and Upper Manhattan this month.

It also was slated to begin auctioning off 2,000 yellow cab medallions in July, a lucrative venture that the city predicted would bring in $1 billion in fiscal year 2013.